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International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3004
Dispersion Compensation Module for WDM -PON at 5 -Gb/s
Downstream with Various Data Modulation
Nidhi Agarwal , Deepak Bansal
Electronics and Communication, Global Institute of Technology, Jaipur,India
Department of Electronics and Communication Engineering, Global Institute of Technology, Jaipur ,India
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ABSTRACT - A Study of Different kind of modulation
format has been discussed to increase the data speed in
PON. Wavelength division multiplexing (WDM) is
commonly employed to utilize this enormous capacity. A
typical transmission system consists of an array of lasers
with different wavelengths to generate the optical
carriers. Each laser is modulated by an external modulator
(e.g. a Mach–Zehnder modulator) to impress the data
signal. The Simulation has been done at 5-Gb/s in optical
communication system with different transmission
distance. The famous of DPSK technique and Dubinary
modulation are used for good tolerance to chromatic
dispersion. It can achieve the high-spectral efficiency
necessary to transmit 10 GB/s data on 50 GHz channel
spacing. A duobinary implementation followed due to the
higher tolerance to accumulated chromatic dispersion.
Further improvements led to the use of differential phase
shift keying (DPSK) with interferometric detection. The
combination of SMF length 87.5 km and DCF length 12.5
km was chosen for total 100 km fiber length. The BER and
Q factor have been used for evaluating the system.
KEY WORDS—Dispersion Compensated Fibers (DCF),
Optical Modulation, Wavelength - Division Multiplexing
(WDM).
1 . INTRODUCTION
The rapid growth in demand for high-capacity
telecommunication links and efficient utilization of fiber
bandwidth has resulted in an extraordinary increase in
the use of Wavelength Division Multiplexing (WDM) in
advanced lightwave networks. The main advantages of
having a last mile of optical fiber are many higher
bandwidth, longer distances from the central to the
subscriber, the more resistance to electromagnetic
interference, increased security, reduced signal
degradation . Optical fiber communication is method of
transmitting information from one place to another by
sending pulse of light. To convey information over any
distance a communication system is usually required.
Fiber optics is a branch of optics which deals with the
transmission of light through fiber glass, plastic or other
transparent materials. Within a communication system
the information transfer is frequently achieved by
superimposing the information on to an electromagnetic
wave. The Basic need of a communication system is its
information –carrying capacity. The basic optical
communication link consists on following four basic
components [4]. The optical transmitter is used to
generate light signal and modulate information on the
signal, the optical fiber is the transmission media of light,
the optical receiver receives the transmitted signal and
converts it back to the carried information and the
optical amplifier is used to extend the transmission
distance. In advance optical communication link /
system, in addition to the above four devices, more
components are required. Optical fibre is used by
telecommunication company such a internet, cable
television telephone.[3]
2. MODULATION METHODS
The optical power is modulated according to the binary
data input signal. Two main types of line codes are
usually employed return to zero (RZ) and non-return to
zero (NRZ) formats. In RZ formats, the signal amplitude
returns to zero at the boundaries of each bit slot, even if
consecutive marks are sent whereas in NRZ format the
signal amplitude remains on the high level in the case of
consecutive marks . Duobinary modulation is a special
partial-response code. It can be generated from a binary
NRZ signal by delay-and-add coding or low pass filtering
. Modulation method was used for transmission rates of
up to 5 Gb/s on/off keying or OOK for short. An
important advantage of using the coherent detection
technique is that both the amplitude and phase of the
received optical signal can be detected and measure. [1]
(a) BPSK (Binary phase shift keying ) : BPSK is the most
efficient of the three digital modulation. Binary phase
shift keying is used for high rates . In BPSK phase of
sinusoidal carrier is changed according to the data bit to
be transmitted. NRZ signal is used to represent the
digital data coming from the digital source. Binary ‘1’is
to be transmitted +1. and Binary ‘0’ is to be transmitted -
1. Phase change is usually a fixed phase shift in the
transmitted.
(b) DPSK (Differential Phase shift Keying): Differential
Phase shift Keying is Differentially coherent modulation
method . DPSK encodes information on the binary phase
change between adjacent bits. A mark is encoded onto a
pie phase change, whereas a zero is represented by the

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International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3005
absence of a phase change DPSK the phase of the
modulated signal is shifted relative to the previous signal
element. The signal phase follows the high or low state of
the previous element. This DPSK technique doesn’t need
a reference oscillator. DPSK encodes two distinct signals,
that is the carrier and the modulating signal with 180°
phase shift each. Symbol ‘0’ may be used to represent
transition in a given binary sequence and symbol ‘1’ to
indicate no transition [5].
(c) OOK (on-off keying): ON-OFF keying (OOK) is
simplest digital modulation technique that represents
digital data. OOK is more spectrally
efficient than frequency-shift keying but more sensitive
to noise when using a regenerative receiver or a poorly
implemented super heterodyne receive. Its return-to-
zero (RZ) version improves the clock recovery by
making the signal return to zero in the middle of the bit
period so a constant stream of one would be represented
by an alternating signal . The bit stream is also
scrambled to avoid long streams of zeroes. There is only
one unit energy carrier and It is switched on or off
depend upon the input binary sequence. Higher
amplitude is represented by logic 0. And lower
amplitude is represented by logic 1 [2].
* Dispersion compensation fiber:
Dispersion compensation fiber is used in many
countries, existing million of kilometer of single mode
fiber in undergoes duct operate at 1.3 micro meters. A
short length of DCF can be used in conjunction with the
1.3 micrometer optimized fiber length so as to have
much lower total dispersion over the entire length. If
these fiber are operated at 1.55 micrometer, there will
be a significant residual dispersion.[6]
3. SIMULATION SET UP
In optical long-haul transmission networks mainly
coherent continuous-wave (CW) lasers are used. A CW
signal produced by Distributed feedback laser (DFB) is a
laser diode at wavelength of 193.1 nm. Semiconductor
lasers are by far the most popular light source for optical
communication systems . Semiconductor lasers are
compact and usually only a few hundred micrometers in
size Frequently used are DFB (distributed feedback)
lasers, which are made of InGaAsP (indium gallium
arsenide phosphide) for the required wavelength range.
DFB lasers can be tuned by varying the forward-bias
current, which changes the refractive index. However,
changing the bias current also changes the output power
of the device and makes this technique unsuitable Lasers
are usually not directly modulated to suppress the
chirping of the emission wavelength, which is especially
detrimental at higher bit rates . Instead, external
modulators are used e.g. optical Mach–Zehnder
modulators MZMs can be implemented in Lithium
Niobate (LiNbO3), Gallium Arsenide (GaAs) or Indium
Phosphide (InP) the high bandwidth of the fiber can be
utilized efficiently by employing a multitude of
transmitters using different wavelengths. This
transmission scheme is called wavelength division
multiplexing (WDM). Simulation has been set up on 5-
Gb/s use RZ and NRZ Duo binary modulation. the
optical signal is attenuated by the optical fiber and other
components such as multiplexers and couplers, it has to
be re-amplified after some distance. Instead also so-
called regenerators may be deployed, which receive the
signal and retransmit it again Fig.[1-6]. Amplifer is a
electronics device that can increase the power of signal
—a delay line interferometer (DI) is inserted in the
optical path at the receiver to convert the differential
phase modulation into intensity modulation A DI can be
used to convert the differential phase modulation into
intensity modulation. Same process of the Intensity
modulation and the Amplifier work on 20dB gain.
Delay Infer meter is 0.2 ns is used. Various wavelength
work on SMF and DCF.
Fig.1. Manchester DPSK with 5-Gb/s downstream
Fig .2. NRZ DPSK with 5-Gb/s downstream
D
F
B
L
a
s
e
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Phase
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PRB
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or
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Phas
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International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3006
Fig. .3. Manchester OOK with 5-Gb/s downstream
Fig. 4. NRZ OOK with 5-Gb/s downstream
Fiber section : The optical signal is fed into the fiber.
Two segment have been used SMF of length L1 km and
DCF L2 km in entirely fiber 100 km. L1 and L2 are used
variables. Table [1-5].
Table 1.
Table 2.
Table 3.
Variation of BER with SMF -DCF length
SMF length
in km(L1)
DCF length in km(L2) BER
100 0 5.0119e-010
97.5 2.5 8.0432e-012
95 5 9.9871e-014
92.5 7.5 7.7079e-015
90 10 4.4199e-012
87.5 12.5 8.3088e-015
85 15 9.91e-014
82.5 17.5 9.90862e-013
Variation of BER with SMF –DCF length
SMF length in
km(L1)
DCF length in
km(L2)
BER
100 0 4.5933e-010
97.5 2.5 6.955e-011
95 5 1.557e-013
92.5 7.5 2.71194e-014
90 10 7.0262e-014
87.5 12.5 4.624e-017
Variation of BER with SMF –DCF length
SMF length in
km(L1)
DCF length in
km(L2)
BER
100 0 5.4651e-007
97.5 2.5 5.651e-008
95 5 2.2559e-009
92.5 7.5 4.718e-011
90 10 2.52639e-010
87.5 12.5 1.0307e-009
85 15 3.6240e-010
D
F
B
L
a
s
e
r
I
M
Manc
heste
r
Phas
e
Dete
ctor
B
E
R
I
M
PRB
S
N
R
Z
Ph
as
e
De
tec
tor
B
E
R
D
F
B
L
a
s
e
r
I
M
NRZ
Phas
e
Dete
ctor
B
E
R
I
M
PRB
S
N
R
Z
Ph
as
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De
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B
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4.
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3007
Table 4
Fig.5 Q factor vs receive power for downstream signal
DPSK use Manchester withDCF
Fig.6 Q factor vs received power for downstream DPSK
use NRZ with DCF
Fig.7 Q factor vs receive power for downstream IM use
Manchester with DCF
Fig.8 Q factor vs receive power for downstream signal IM
use NRZ with DCF
4. RESULT CONCLUSION
The performance of the system is evaluated using the
parameters, BER and Q factor, with pre, post and
symmetrical compensation techniques using DCF at
various link lengths .The main advantage compared to
NRZ-OOK is a 3 dB receiver sensitivity improvement,
which can be intuitively understood from the increased
symbol spacing for DPSK compared to OOK for fixed
average optical power This signal format furthermore
shows better behavior regarding signal distortions due
to fiber nonlinearities especially excellent resilience to
cross-phase modulation . NRZ can be travelled till longer
distance without DCF , Therefore NRZ is better than
Manchester. NRZ and Manchester are worked on various
wavelength. . Better performance is shown when a
combination of SMF length 87.5 km and DCF length 12.5
km was chosen for total 100 km fiber length.
Variation of BER with SMF -DCF length
SMF length in
km(L1)
DCF length in
km(L2)
BER
100 0 8.1335e-009
97.5 2.5 2.7565e-010
95 5 4.3197e-013
92.5 7.5 1.5772e-014
90 10 1.385e-016

5.
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3008
REFERENCE
[1] “Comparison of RZ Versus NRZ Pulse Shapes for
Optical Duobinary Transmission”, Cheng-Chung Chien
and Ilya Lyubomirsky, Journal Of Lightwave Technology,
Vol. 25, No. 10, October 2007.
[2] “Advanced Modulation Formats for Ultra-Dense
Wavelength Division Multiplexing”, Dr. Ilya Lyubomirsky
2005.
[3] Kuschnerov, M., Hauske, F.N., Piyawanno, K., Spinnler,
B., Alfiad, M.S., Napoli, A., Lankl, B.: DSP for coherent
single-carrier receivers. IEEE/OSA J. Lightw. Technol.
27(16), 3614–3622 (2009)
[4] M. I. Hayee and A. E. Willner, “Pre- and post-
compensation of dispersion and nonlinearities in 10-
Gb/s WDM systems”, IEEE Photon. Tech. Lett. 9, pp.
1271, 1997.
[5] Design Performance of High Speed Optical Fiber
WDM System with Optimally Placed DCF for Dispersion
Compensation. Yadav, Mulayam, et al. 20, s.l. :
Foundation of Computer Science, 2015, International
Journal of Computer Applications, Vol. 122.
[6] Dispersion Compensation with Dispersion
Compensating Fibers (DCF). Kaur, Manpreet, Sarangal,
Himali and Bagga, Parveen. 2015, International Journal
of Advanced Research in Computer and Communication
Engineering.